Fast calculation method for CGHs using spherical pre-calculated object light

Hologrpahy is a three-dimensional technology. Light waves from an object are recorded and reconstructed using holograms. computer generated hologram (CGH) is performed by computer simulation. However, an enormous amount of computational time is required for calculating CGHs. This paper is focused on high speed calculation for CGH. There are the two main methods for calculating CGH, such as the point light method and the method based on Fourier transforms. The point light method calculates light waves from objects but requires an enormous amount of computation time. The other methods based on Fourier transforms calculates using a fast Fourier transform algorithm, and the calculation speed is faster than one of the point light method. However, the calculation for complex objects requires many FFTs, so the computational time is enromous. To improve the problem, we have proposed a fast calculation method for computer generated holograms that uses cylindrical pre-calculated object light.(9) This method does not require a FFTs. Cylindrical pre-calculated object light is made by calculating light waves from a basic object on a semi-circle cylinder. This method calculates the light of arbitrary object shapes by transforming pre-calculated object light. However, a large amount of memory is required. In this paper, to improve this method, we reduce this memory requirement by using sherical pre-calculated object light. We achieved a transfer distance from an object to a hologram by using spherical pre-calculated object light. Moreover, the computational time of our method is reduced by using graphics processing units.